Or at least I wouldn't think it would be a range of anywhere like "$20-$75"

More of a range than you might think. Again, it depends on how you want it sent. 20 discs with packaging I'm figuring about 9 pounds. USPS Priority mail for that weight can range from $11.85 to $33.55 depending on destination. You will probably find similar spreads on UPS or Fedex's charts.